An RRU is a module capable of conversion between a radio frequency signal and a digital signal in a radio base station. To reduce loss of the radio frequency signal transmitted on a cable (from or to an antenna), the RRU needs to be installed as close to the antenna as possible, and is generally installed on the top of a transmitting tower or a building.
Because the frequency of radio frequency signals processed by an RRU varies, RRUs of different bands exist. Under the current technical conditions, an RRU generally supports one band. Currently, most radio communication operators generally own multiple bands. Under the multi-band circumstances, an operator has to deploy multiple RRUs to provide multi-band communication services. Generally, an RRU is installed in a chassis. Therefore, multiple chassis are needed in order to install multiple RRUs. The operator generally rents a tower for installing a chassis and the RRU in it, and the tower owner generally collects a rent according to the number of chassis. Therefore, installation of multiple chassis brings huge operation costs.
A common solution is to install multiple RRUs in a large chassis to make up a large RRU that supports multiple bands. In such a solution, a chassis is installed first, and then RRUs of different bands are installed in the chassis. However, the solution is costly because the number of RRUs installed in a chassis varies depending on different circumstances. If uniform chassis are applied to facilitate manufacturing, the space in some chassis will be idle.